1. Field of the Invention
This invention relates generally to valves and more particularly to a bypass valve which senses a predetermined differential pressure disposed thereacross and in response thereto opens to relieve the pressure and permit fluid flow therethrough and which also provides an indication that the relief valve has responded to the excess pressure and is in the bypass position.
2. The Prior Art
There are many bypass valves existing in the prior art which in response to a predetermined pressure differential thereacross will open to relieve that pressure and permit fluid flow. These bypass valves take many forms including that of the typical poppet valves. One typical application for such bypass valves is in conjunction with a fluid filter. As the filter element becomes dirty through entrapment of foreign particles suspended within the fluid that is being filtered the pressure between the inlet and the outlet of the filter increases. The increased pressure differential is indicative that the filter element needs replacing or cleaning. If the element is not replaced or cleaned, the increased pressure may ultimately destroy the filter element, or, in the case a bypass valve is installed, will allow unfiltered fluid to enter the operating apparatus with the possibility of ultimate destruction thereof.
Insofar as is known to applicant, prior art bypass valves are of the type which respond to the differential pressure and then crack or open a desired amount to permit fluid flow therethrough. Although such operation is appropriate, under some circumstances, it is also desired that an immediate release of the differential pressure be obtained. Under such conditions a differential area bypass valve has been used to insure an immediate pressure relief.
Furthermore, in the prior art there are many devices which provide an indication to the operator (visual and/or electrical) of overpressure. Applicant, however, is unaware of any prior art devices which, in the same structure, include immediate pressure relief, overpressure and bypass state indication, along with appropriate structure to ensure actuation of the bypass indication mechanism.